ghost-rider rotates through user-defined options in a Ghostty config file.

ghost-rider.go

// ghost-rider rotates options inside a Ghostty config file.

// It expects the config file to have a specific format, where options are defined
// in a comment line starting with "# gr: " followed by a comma-separated list of
// options, and the actual option line that follows it. The script will rotate
// the option to the next one in the list each time it is run.
// The specific option to rotate can be specified with the -opt flag.

// Invoking this with a hotkey manager such as skhd allows for easy
// cycling through options like themes or background opacity in ghostty.
// The script tells Ghostty to reload its configuration after modifying the file.

// The compiled version of this binary and the skhd helper will need to be added
// to the assistive access list in System Settings >> Privacy & Security >> Accessibility.

// Config for https://github.com/koekeishiya/skhd
// cmd + shift - p : ~/.local/bin/ghost-rider -opt theme
// cmd + shift - b : ~/.local/bin/ghost-rider -opt background-opacity

/*
Example ghostty config snippet:

# gr: 0.75,0.9,1.0,0.5,0.6
background-opacity = 0.75

# gr: Adwaita,Japanesque
theme = Japanesque
*/

package main

import (
	"flag"
	"fmt"
	"os"
	"strings"

	"github.com/andybrewer/mack"
)

var (
	cfg = flag.String("fn", "~/.config/ghostty/config", "config file path")
	opt = flag.String("opt", "theme", "option to rotate")
)

func main() {
	flag.Parse()

	// Expand the config file path, subsituting ~ with the home directory
	homeDir, err := os.UserHomeDir()
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error getting home directory: %v\n", err)
		os.Exit(1)
	}
	*cfg = strings.ReplaceAll(*cfg, "~", homeDir)

	conf, err := os.ReadFile(*cfg)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error reading config file: %v\n", err)
		os.Exit(1)
	}
	lines := strings.Split(string(conf), "\n")

	// Example stanza from the ghostty config file:
	// # gr: 0.75,0.9,1.0,0.5,0.6
	// background-opacity = 0.75

	// Look for the line that starts with the option.
	for i := range len(lines) - 1 {
		if !strings.HasPrefix(lines[i], "# gr: ") {
			continue
		}
		opts := strings.Split(lines[i][6:], ",")
		parts := strings.Split(lines[i+1], "=")
		if len(parts) != 2 {
			continue
		}
		parts[0], parts[1] = strings.TrimSpace(parts[0]), strings.TrimSpace(parts[1])
		// check if the line before the comment is the option we want to rotate
		if parts[0] != *opt {
			// fmt.Fprintln(os.Stderr, "Skipping line:", lines[i-1])
			continue
		}
		for j, o := range opts {
			if o == parts[1] {
				// rotate to the next option
				nextOpt := opts[(j+1)%len(opts)]
				lines[i+1] = fmt.Sprintf("%s = %s", parts[0], nextOpt)
				break
			}
		}
	}

	// Write the modified config back to the file
	err = os.WriteFile(*cfg, []byte(strings.Join(lines, "\n")), 0o644)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error writing config file: %v\n", err)
		os.Exit(1)
	}

	mack.Tell("System Events",
		`tell process "Ghostty"`,
		`click menu item "Reload Configuration" of menu "Ghostty" of menu bar item "Ghostty" of menu bar 1`,
		`end tell`)
}